Good concept, poorly executed.

Simple and well acted, it has tension enough to knot the stomach.

A lot of perfectly good film show their cards early, establish a unique premise and let the audience explore a topic at a leisurely pace, without much in terms of surprise. this film is not one of those films.

A film with more than the usual spoiler issues. Talking about it in any detail feels akin to handing you a gift-wrapped present and saying, "I hope you like it -- It's a thriller about a diabolical secret experiment."